This invention relates to the field of energy conservation, and particularly to means for reducing the loss of heat known to take place at the windows and other openings of buildings.
The provision of at least one window in a wall of each principal room in a house is desirable to provide natural light during the daylight hours, to maintain occupants of the rooms in communication with the world outside, and if necessary to provide emergency egress from the rooms. In general, the windows are arranged to open, at least in part, by "casement" or "double hung" construction, to accomplish ventilation of the rooms by admission of ambient outside air, and in most areas screens are a necessary adjunct to keep out airborne objects, insects, bats, and so forth.
Equally necessary as adjuncts, particularly in areas of less temperate climate, are storm windows, which function to permit entry of light while creating a dead air space to reduce heat transmission during the winter. The former routine of taking off storm windows and substituting screens in the spring, with the reverse procedure in the fall, is being replaced by the use of "combination" windows, which can serve either as storms or as screens, but some form of energy conservation is still necessary to prevent heating costs from rising intolerably in the winter.
Storm windows, whether elementary or "combined", are arranged to fit into the frames of the house windows, which have ledges at the top and sides for that purpose. Particularly with the more elementary arrangements, it is found that they perform their function only imperfectly. Even the most perfect workmanship seldom results in a space of truly dead air, and only slight leakage is required to materially reduce the efficiency of the arrangement. While the more modern arrangements are perhaps more perfect initially, the dimensional changes which occur in all buildings with age soon result in the appearance of small passages for movement of air into and out of the supposed dead space, with the related loss of efficiency.